Production of fermentation products, such as ethanol, from starch-containing material is well-known in the art. Generally two different kinds of processes are used. The most commonly used process, often referred to as a “conventional process”, includes liquefying gelatinized starch at high temperature using typically a bacterial alpha-amylase, followed by simultaneous saccharification and fermentation carried out in the presence of a glucoamylase and a fermenting organism. Another well-known process, often referred to as a “raw starch hydrolysis”-process (RSH process) includes simultaneously saccharifying and fermenting granular starch below the initial gelatinization temperature typically in the presence of an acid fungal alpha-amylase and a glucoamylase.
U.S. Pat. No. 5,231,017-A discloses the use of an acid fungal protease during ethanol fermentation in a process comprising liquefying gelatinized starch with an alpha-amylase.
WO 2003/066826 discloses a raw starch hydrolysis process (RSH process) carried out on non-cooked mash in the presence of fungal glucoamylase, alpha-amylase and fungal protease.
WO 2007/145912 discloses a process for producing ethanol comprising contacting a slurry comprising granular starch obtained from plant material with an alpha-amylase capable of solubilizing granular starch at a pH of 3.5 to 7.0 and at a temperature below the starch gelatinization temperature for a period of 5 minutes to 24 hours; obtaining a substrate comprising greater than 20% glucose, and fermenting the substrate in the presence of a fermenting organism and starch hydrolyzing enzymes at a temperature between 10° C. and 40° C. for a period of 10 hours to 250 hours. Additional enzymes added during the contacting step may include protease.
WO 2010/008841 discloses processes for producing fermentation products, such as ethanol, from gelatinized as well as un-gelatinized starch-containing material by saccharifying the starch material using at least a glucoamylase and a metalloprotease and fermenting using a yeast organism. Particularly the metallo protease is derived form a strain of Thermoascus aurantiacus. 
WO 2014/037438 discloses serine proteases derived from Meripilus giganteus, Trametes versicolor, and Dichomitus squalens and their use in animal feed.
WO 2015/078372 discloses serine proteases derived from Meripilus giganteus, Trametes versicolor, and Dichomitus squalens for use in a starch wet milling process.
S53 proteases are known in the art. A S53 peptide from Grifola frondosa with accession number MER078639. A S53 protease from Postia placenta (Uniprot: B8PMI5) was isolated by Martinez et al in “Genome, transcriptome, and secretome analysis of wood decay fungus Postia placenta supports unique mechanisms of lignocellulose conversion”, 2009, Proc. Natl. Acad. Sci. USA 106:1954-1959.
Vanden Wymelenberg et al. have isolated a S53 protease (Uniprot: Q281W2) in “Computational analysis of the Phanerochaete chrysosporium v2.0 genome database and mass spectrometry identification of peptides in ligninolytic cultures reveal complex mixtures of secreted proteins”, 2006, Fungal Genet. Biol. 43:343-356. Another S53 polypeptide from Postia placenta (Uniprot:B8P431) has been identified by Martinez et al. in “Genome, transcriptome, and secretome analysis of wood decay fungus Postia placenta supports unique mechanisms of lignocellulose conversion”, 2009, Proc. Natl. Acad. Sci. U.S.A. 106:1954-1959.
Floudas et al have published the sequence of a S53 protease in “The Paleozoic origin of enzymatic lignin decomposition reconstructed from 31 fungal genomes”, 2012, Science, 336:1715-1719. Fernandez-Fueyo et al have published the sequences of three serine proteases in “Comparative genomics of Ceriporiopsis subvermispora and Phanerochaete chrysosporium provide insight into selective ligninolysis”, 2012, Proc Natl Acad Sci USA. 109:5458-5463 (Uniprot:M2QQ01, Uniprot:M2QWH2, UniprotM2RD67).
It is an object of the present invention to identify proteases that will result in an increased ethanol yield in a starch to ethanol process, when said proteases are added/are present during saccharification and/or fermentation.